The Lionel 0-6-0 Docksider LC+2.0 is a great engine for the price point and can be modified some. I needed just a bit more speed out of mine but going too fast causes the chuffs to sound like a skipping CD. I don't know the details of why that is but it's all good. There's a way around it.
This is a permanent mod and it's probably not good for your warranty.
You will cut your chuff rate in half and that is less realistic. I didn't care because there really aren't a lot of people that even know there should be four chuffs per revolution. So it's all the same to me.
Step 1: Remove the screws that the red arrows are pointing at. There are plastic plates under your pickup rollers. They might stick to the rollers or they might need convinced to come out with an o-ring pick or small screwdriver.
Step 2: Lay your screws out approximately where they go. Then use that o-ring pick or a small screwdriver to pop the bottom plate (yellow arrow) off. My locomotive had a lot of grease under the plate and I spilled smoke fluid on it. So everything was oily and sticking together.
Watch your hands here. The drivers are all free to pop upwards (towards you) now. That's not a major issue if it happens but pay attention to the orientation of the parts on the axle so you can figure out how to put it back together. The middle set of wheels are sprung and there is nothing besides grease holding the springs in place so you may very well pull the spring out if you pop the middle wheels up. I did. The spring came out and had to be carefully set back in its hole with a small pair of needle nose pliers.
Step 3: Hopefully you avoided popping the axles up. You'll now need that fancy little wrench that came with your locomotive that you probably threw away. I did. Take the bolts from the rear most drive wheels out (yellow arrow). There is a little bushing there (red arrow points at it). Don't lose that.
Step 4: Now look where the green arrow is pointing in the picture below. I couldn't get a great picture but there is a black plastic piece therewith 4 little pegs sticking out of it. The pieces are on a ring that attaches to the axle. Each litte peg is spaced 90* apart. This is your chuff generator. You're going to cut two of these off. I recommend you get a small pair of needle nose pliers and grab one, then snip it off at the bottom where it meets the plastic ring that is on the axle. Do NOT cut that plastic ring that is on the axle. Otherwise you will have no chuff. You are only removing the part that is sticking out. There is a picture of what you should take off named S4-2. Once you clip off your first piece, you need to spin the axle 180* to cut the opposite piece off. So you make your cut, set that piece aside. Spin the axle so you skip the next little piece, then cut the piece after that. Hopefully I have explained that enough. Ask below if I didn't. You should have two pieces left on the ring, situated opposite each other (180*).
Step 5: Now spin your axle backwards to get it to the position you started in so you can reattach your drive rods. Then reassemble everything you took off.
You'll have less chuffs when you put it back on the track. That will be less realistic but you'll be able to go a little faster without overwhelming the sound system. You'll also get a slightly pronounced puff of smoke at super slow speeds but it's not anything impressive, it's just an improvement.
You probably could glue the pegs back but I think it would be difficult. It would be particularly difficult if you didn't manage to de-grease the area.
But that's how I got a little bit more speed out of my 0-6-0 LC+2.0 locomotive. Now I gotta get new side rods (Lionel P/N: 620-8613-320), fix the pesky rear coupler, and detail the inside a bit. But those are projects for another day. Let me know if I wasn't clear anywhere.
Edit 2/22/2021: I added two videos. I tried to capture the smoke puff in one. It's subtle but there. The other just shows the chuff during operation. Excuse the chaotic test layout haha
Edit 2/27/2021: I remove the two videos and added a much better video. This video also includes the installed siderods that make it run better. Lionel P/N: 620-8613-320. Credit to @gunrunnerjohn for that part number.